When performing data processing by a plurality of information processing terminals, a file server (storage device) typically handles centralized data management in order to increase the efficiency of maintenance and management of data. The file server may be a Network Attached Storage (NAS) device, for example.
A NAS device collectively manages many storage media using Redundant Array Inexpensive (Independent) Disks (RAID) or the like, thereby improving the reliability of data and providing a large-capacity storage area. A NAS device may use Hard Disk Drives (HDDs), semiconductor-memory SSDs (Solid State Drives: flash memory drives), or the like, as storage media. Here, an SSD has a faster access performance than an HDD and is particularly superior in terms of random read performance. In addition, despite their low power consumption, low heat radiation, and high shock resistance, SSDs have disadvantages such as higher price per capacity than HDDs, and limitation on the number of writable times (for example, see Japanese Laid-open Patent Publication No. 2008-40713).
A NAS device ensures data protection using parity data in the event of a failure of an SSD included in a RAID (e.g., RAID 4, RAID 5) due to usage exceeding the number of writable times (for example, see Japanese Laid-open Patent Publication No. 10-269032, and Japanese Laid-open Patent Publication No. 2010-15516).
However, storage devices, including NAS devices, have a risk of losing data in the event of a failure of two or more SSDs included in a RAID.